Doctors in Gaza have reported previously unseen injuries from Israeli weapons that cause severe burning and leave deep internal wounds, often resulting in amputations or death.

The injuries were first seen in July, when Israel launched operations in Gaza following the capture of an Israeli soldier by Palestinian militants.

Doctors said that, unlike traditional combat injuries, there was no large shrapnel found in the bodies and there appeared to be a "dusting" on damaged internal organs.

"Bodies arrived severely fragmented, melted and disfigured," said Jumaa Saqa'a, a doctor at the Shifa hospital, in Gaza City. "We found internal burning of organs, while externally there were minute pieces of shrapnel. When we opened many of the injured people we found dusting on their internal organs."

It is not clear whether the injuries come from a new weapon. The Israeli military declined to detail the weapons in its arsenal, but denied reports that the injuries came from a Dense Inert Metal Explosive (Dime), an experimental weapon.

In Gaza, Dr Saqa'a said the small pieces of shrapnel found in patients' bodies did not show up under x-ray. "We are used to seeing shrapnel penetrate the body making localised damage. Now we didn't see shrapnel, but we found the destruction," he said.

Most of the injuries were around the abdomen, he said. The doctors also found that patients who were stabilised after one or two days suddenly died. "The patient dies without any apparent scientific cause," he said.

At the Kamal Odwan hospital, in Beit Lahiya, the deputy director, Saied Jouda, said he had found similar injuries. "We don't know what it means - new weapons or something new added to a previous weapon," he said. He too found patients with severe internal injuries without signs of any large shrapnel pieces. "There was burning, big raw areas of charred flesh," he said. "This must be related to the type of explosive material."

Photographs of some of the dead from Shifa hospital showed bodies that had been melted and blackened beyond recognition. In several cases doctors amputated badly burnt limbs.

At least 250 Palestinians have died in Gaza since the latest military operations began and hundreds more have been injured.

Neither of the doctors could give exact figures for the numbers of patients suffering the new injuries, although both said that most of those brought in during July showed signs of these injuries.

Dr Saqa'a said the injuries occurred over six weeks beginning in late June, while Dr Jouda said he believed patients admitted even in recent days still showed signs of unusual injuries.

The health ministry in Gaza reported that these injuries came from an "unprecedented type of projectile," and also noted severe burning and badly damaged internal organs. It called for an investigation into the cause of the wounds.

"You have complete burns that lead to amputation. You find shrapnel entering the body and leaving very, very small holes. We have never seen this before," said Khalid Radi, a spokesman at the health ministry.

Tissue samples from patients in Gaza were given to journalists from the Italian television channel RAI. In a documentary shown last week, the channel said the injuries appeared similar to the effects of Dime. An Italian laboratory that analysed the samples reportedly said its results were compatible with the hypothesis that a Dime weapon was involved.

The weapon is new and in the US it is still in the early stages of development. It has a carbon-fibre casing and contains fine tungsten particles rather than ordinary metal shrapnel. It causes a very powerful blast, but with a much more limited radius than other explosives.

However, the Israeli military denies the use of Dime weapons.

"The defence establishment is investing considerable effort to develop weaponry in order to minimise the risk of injury to innocent civilians. With regard to allegations of the use of Dime weaponry, the Israel defence forces deny the possession or use of such weapons," the military said in a statement. "Due to operational reasons, the IDF cannot specify the types and use of weapons in its possession. In addition it should be emphasised that the IDF only uses weapons in accordance with the international law."

Some Israeli military experts have also dismissed the suggestion that a Dime weapon is involved.

Isaac Ben-Israel, a professor at Tel Aviv University and a retired Israel air force general who was involved in weapons development, had seen some of the photographs of the dead and injured and said he believed that the wounds came from ordinary explosives. "I can tell you surely that no one in Israel ever developed such a Dime weapon. It doesn't exist at all," he said.

The International Committee of the Red Cross, which monitors weapons used in conflicts, said it had heard reports of similar injuries from Gaza and was collecting information on the case. "We haven't come to any sort of conclusion about what kind of weapon it was," said Bernard Barrett, an ICRC spokesman.